Ito's lemma for the log of a GBM with mu 3, sigma 4

Suppose a price follows $dS_t=3S_t\,dt+4S_t\,dW_t$ for a standard Brownian motion $W$. The log-price $X_t=\ln S_t$ then satisfies $dX_t=a\,dt+b\,dW_t$ for constants $a,b$. Compute $a^2+b^2$.

$41$. Ito's lemma on $\ln x$ gives $dX_t=(\mu-\tfrac12\sigma^2)dt+\sigma\,dW_t=(3-8)dt+4\,dW_t$, so $a=-5$, $b=4$ and $a^2+b^2=25+16=41$.